The present invention relates to an intake valve control system and method for an internal combustion engine.
Various types of intake valve control systems of internal combustion engines have been proposed to secure improved fuel economy and stable running performance during low-speed low-load engine operation and to secure sufficient power output with improved intake efficiency during high-speed high-load engine operation. Among others, Japanese Laid-Open Patent Publication No. 2001-263105 proposes an intake valve control system for an internal combustion engine, which includes an angle control mechanism for varying an operation angle of an engine intake valve and a phase control mechanism for varying a maximum lift phase of the intake valve. The angle and phase control mechanisms are operated independently of each other in accordance with engine operating conditions so as to control the operation angle and maximum lift phase to their respective target values and thereby adjust an intake air amount appropriately for improvements in fuel economy and power output.